[Solved] sorting not working magento 2

Ram Pratap Singh Gour Asks: sorting not working magento 2
I created a custom column “product_name” in sales/order grid,

When I am sorting this column grid showing error:

Item (MagentoFrameworkViewElementUiComponentDataProviderDocument) with the same id “146” already exist

My collection code is :

        $joinTable = $this->getTable('mg_dispatch_date');
        $joinTable2 =$this->getTable('customer_entity_varchar');
        $joinTable3 = $this->getTable('catalog_product_entity_varchar');
        $this->getSelect()->join($joinTable . ' as mdd', 'main_table.entity_id = mdd.order_id', array('*')); 
        $this->getSelect()->join($joinTable2. ' as fn', 'main_table.customer_id = fn.entity_id and fn.attribute_id = 177',array('value'));
       $this->getSelect()->join($joinTable3.' as cpev','main_table.entity_id = cpev.entity_id', array('*'));  
        return $this;

and sales_order_item.xml code is :

<column name="product_name" class="MagecoderCustomerrefUiComponentListingColumnProductname">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">

            <item name="filter" xsi:type="boolean">false</item>
            <item name="sortable" xsi:type="boolean">true</item>
                    <item name="bodyTmpl" xsi:type="string">ui/grid/cells/html</item>
                    <item name="visible" xsi:type="boolean">true</item> 
                    <item name="label" xsi:type="string" translate="true">Product Name</item>

Please help is anyone have suggestion, Thanks in Advance.

Ten-tools.com may not be responsible for the answers or solutions given to any question asked by the users. All Answers or responses are user generated answers and we do not have proof of its validity or correctness. Please vote for the answer that helped you in order to help others find out which is the most helpful answer. Questions labeled as solved may be solved or may not be solved depending on the type of question and the date posted for some posts may be scheduled to be deleted periodically. Do not hesitate to share your response here to help other visitors like you. Thank you, Ten-tools.